Many Londoners were awoken by a loud “bang” at around 4:15 a.m. on Monday morning, which prompted many to take to social media, post what they heard and look for  answers.

The massive sound left many worrying that London may have been the scene of a terror attack or tragic accident, with local police even issuing a statement through Twitter acknowledging that they were looking into these reports. It wasn’t long, however, before it was confirmed that the massive boom was actually created by two Royal Air Force Typhoon fighters going supersonic over the city in order to intercept a wayward, unresponsive aircraft.

While the majority of the fighter jets employed by the militaries of the developed world are capable of achieving supersonic speeds, by and large, they’re barred from doing so over heavily populated areas over concerns about the damage sonic booms can cause to civilian property.